Unique fiberoptic-based chemical sensors will be developed to measure drugs, toxins, and naturally occurring biochemicals in living systems. This proposal describes and discusses instrumentation and analytical methodologies which integrate fluoroimmunoassay principles with laser-based fiberoptic systems. The described fluoroimmuno sensors (FIS) derive their analytical selectivity through the specificity of antibody-antigen reactions. In this work antibodies are immobilized at the terminus of a fiberoptic within the FIS and assay procedures will ultimately involve in-vivo incubation followed by in-vitro fluorescence measurement. High sensitivity is to be achieved through the combined utilization of europium chelate fluorotags, pulsed laser excitation, and signal recovery using a gated photon counter. Initial in-vitro studies aimed at optimizing the procedures for preparing and using the FIS will employ a commercially available immunochemical system. Subsequent experiments involving the production of antibodies for certain chemical carcinogens, incorporation of these antibodies in FIS, and use of these FIS for actual measurements in laboratory animals are planned to demonstrate the capabilities of this instrumentation. An interdisciplanary approach to the proposed experiments will be pursued throughout this work.